The ACUSITT ultrasonic ablator: The first steerable needle with an integrated interventional tool

Steerability in percutaneous medical devices is highly desirable, enabling a needle or needle-like instrument to avoid sensitive structures (e.g. nerves or blood vessels), access obstructed anatomical targets, and compensate for the inevitable errors induced by registration accuracy thresholds and tissue deformation during insertion. Thus, mechanisms for needle steering have been of great interest in the engineering community in the past few years, and several have been proposed. While many interventional applications have been hypothesized for steerable needles (essentially anything deliverable via a regular needle), none have yet been demonstrated as far as the authors are aware. Instead, prior studies have focused on model validation, control, and accuracy assessment. In this paper, we present the first integrated steerable needle-interventional device. The ACUSITT integrates a multi-tube steerable Active Cannula (AC) with an Ultrasonic Interstitial Thermal Therapy ablator (USITT) to create a steerable percutaneous device that can deliver a spatially and temporally controllable (both mechanically and electronically) thermal dose profile. We present our initial experiments toward applying the ACUSITT to treat large liver tumors through a single entry point. This involves repositioning the ablator tip to several different locations, without withdrawing it from the liver capsule, under 3D Ultrasound image guidance. In our experiments, the ACUSITT was deployed to three positions, each 2cm apart in a conical pattern to demonstrate the feasibility of ablating large liver tumors 7cm in diameter without multiple parenchyma punctures.